books
Google Books API
Google's index of book volumes, covering tens of millions of titles with metadata and, where permitted, previews. You can search by title or ISBN through its API, and a free key raises the otherwise tight request quota. It offers broad coverage for confirming a book's existence and edition details and for finding preview pages.
Por que é útil e como funciona
Google Books is useful for confirming a title exists and for reading previews of recent in-copyright works that no other service shows. You search by title, author, or ISBN and receive metadata, a cover image, and, depending on publisher agreements, a limited or full preview. A free Google Cloud API key is needed for reliable programmatic use; without it, requests are throttled quickly. It is not a source of freely downloadable books but excels as a discovery and verification tool across an enormous range of titles.
O que há dentro
Tens of millions of titles indexed, with varying preview depth from no preview to full text, depending on publisher permissions and copyright status.
Acesso via API
Acesso
Programmatic API access (a key may be required, see the API tag).